Modified Monopole–CDR Hybrid Antenna

This paper presents bandwidth enhancement of a monopole antenna by hybridization with cylindrical dielectric resonator (CDR) elements. Dual resonance of the monopole is obtained when the electric current distribution is controlled by adding metallic branches and metallic sphere components. Two prototypes are proposed, incorporating the dual monopole modes and hybrid automatic (HEM)11δ mode of CDR elements, promising an ultra-wideband (UWB) response with an omnidirectional radiation pattern. The first prototype is composed of two CDRs and a monopole branch which gives an operating bandwidth of 67.25% (6.01–12.1 GHz). The second prototype, with a small metallic sphere-loaded monopole, is surrounded symmetrically by four CDR elements. As a result, the impedance bandwidth is enhanced up to 76.61% (6.2–13.9 GHz). The simulated results including reflection coefficients, radiation patterns, and antenna gains are compared with the experimental results of the fabricated prototype, and good agreement is found between them.